Cannot, Lowey. Powerline devices have to work behind the same electrical circuit, otherwise, they will not be able to communicate with each other properly. What's the distance between two buildings,...

Did you try channel width 40MHz? Besides, did you secure the network with WPA2-PSK, AES?

Did you ever upgrade a third party firmware like DD-WRT? Or maybe you are connecting to a different network wirelessly?

Did you try what fotodamaris or Ada suggested? What's the hardware version and firmware version of your WA7210N?

Harish, the hardware version of your WR740 is v4? Do you know different hardware versions do not share firmware versions? Maybe that's why you cannot successfully upgrade the firmware for v5.

Alex, what's the distance between two routers? Any obstacles? Try to shorten the distance and test if the connection will be stable. "I've seen some places suggest that the WLAN Bridge router should...